Methods for making container bodies using thermoplastic adhesive



April 3, 1969 4 w. R. BATTERSBY 3,437,053

METHODS FOR MAKING CONTAINER BODIES USING THERMOPLASTIC ADHESIVEOriginal Filed July 6, 1965 Sheet of 2 Inventor: M'M'am 3.5a ifersbyApril 8, 1969 w. R. BATTERSBY METHODS FOR MAKING CONTAINER BODIES USINGTHERMOPLASTIC ADHESIVE Sheet 2 012 Jriginal Filed July 6, 1965 UnitedStates Patent 3,437,063 METHODS FOR MAKING CONTAINER BODIES USINGTHERMOPLASTIC ADHESIVE William R. Battersby, Lexington, Mass., assignorto United Shoe Machinery Corporation, Flemington, N..I., a corporationof New Jersey Original application July 6, 1965, Ser. No. 469,513, nowPatent No. 3,329,740, dated July 4, 1967. Divided and this applicationApr. 28, 1967, Ser. No. 634,761

Int. Cl. B21d 51/04, 51/10; B65d 3/04 U.S. Cl. 113-121 8 Claims ABSTRACTOF THE DISCLOSURE A method for making container bodies in whichthermoplastic adhesive having controlled delay hardening ability isapplied to a side seaming surface portion of a metallic container blankand the blank is formed into a tubular body with the adhesive in heatactivated condition between the side seaming surface portion on which itis applied and an opposite side seaming surface portion. Portions, e.g.end edge portions, are deformed e.g. flanged, the adhesive is caused toincrease in hardness and the ends attached to the tubular body.Thereafter, the adhesive is caused to advance further in hardening.

This application is a division of my copending application Ser. No.469,513, filed July 6, 1965, entitled, Thermoplastic Adhesive PreparedFrom Crystallizable Polyester Resin and Amorphous Phenoxy Resin, now US.Patent No. 3,329,740, issued on July 4, 1967.

Field of the invention This invention relates to a method for makingmetallic container bodies including side seaming with a thermoplasticadhesive composition.

Description of the prior art Bonding of metallic surfaces such as theside seams of tubular container bodies traditionally has been effectedby welding, brazing or soldering. Serious difficulties have beenencountered in attempts to use organic adhesives, not

Summary of the invention It is an object of the present invention toprovide a method for making container bodies using organic resin baseadhesive activatably by heat for side seaming metallic container blanks,in which the conditions encountered in the various steps aid indeveloping properties in the adhesive joint for meeting conditionsencountered in succeeding steps.

To this end and in accordance with a feature of the present inventionthermoplastic adhesive is applied in molten condition to side seamingsurface portions, the side seaming portions are brought together withthe adhesive in heat activated condition and thereafter the adhesive iscaused to progress in hardness and strength during the stages ofcompletion of a container body.

3,437,063 Patented Apr. 8, 1969 Brief description of the drawing Theabove and other features of the invention will be more particularlydescribed with reference to the accompanying drawings and pointed out inthe claims. It will be understood that the adhesive method is useful informing adhesive joints other than that involved in the particularcontainer body shown for purposes of illustration.

In the drawings,

' FIG. 1 is a perspective view of a container blank useful in makingcontainer bodies using the method of this invention;

FIG. 2 is an edge view of the sheet shown in FIG. 1 taken in thedirection of the arrow II;

FIG. 3 is a perspective view of a partially completed container bodymade from the blank shown in FIG. 1;

FIG. 4 is an edge view of the seam of the container body of FIG. 3 takenin the direction of the arrow IV;

FIG. 5 is a perspective view of the container body after flanging of theend edges; and

FIG. 6 is a perspective view of a completed container.

It will be appreciated that the various drawings are not necessarilyscale drawings of either the tubular bodies or components thereof buthave been enlarged, modified and portions emphasized to assist inpointing out more clearly various features of the invention.

Description of the preferred embodiments FIGS. 1 and 2 show a body blankB which comprises a flat rectangular sheet of conventional tin plate,i.e. sheet steel plated on both surfaces with tin. The blank also may beof aluminum, other ferrous or nonferrous materials or composite metaland fiber laminates. The upper surface of the blank B, i.e. that whichfaces the viewer in FIG. 1, is designated surface i and the lower oropposite surface is designated 0. They are so designated since these arethe surfaces which will ultimately constitute the inside and outside ofthe tubular body. The rectangular blank has opposite parallel edges 2and 4. Organic thermoplastic adhesive of the type mentioned above isapplied in a band 6 about /4" wide to one or both side seaming margins 8and 10 beginning at the edges 2 and/ or 4.

To form the body, the blank B is bent or curved into tubularconfiguration (usually but not necessarily cylindrical) about a centrallongitudinal axis A (FIG. 3) with the opposed parallel edges 2 and 4 andtheir adjacent side seaming margins 8 and 10 overlapping and theadhesive band or bands 6 disposed between the side seaming margins. Theamount of overlap (designated generally as L in FIG. 4) is approximatelyA" measured circumferentially of the body. In its tubular configurationthe seaming margin 8 engages the side seaming margin 10 on outer surface0 of the body. The side seaming margins are then held together and heatis applied to reactivate the adhesive to form a lap seam S. Upon coolingthe seam S is completely sealed.

FIG. 5 shows the resulting side seamed tubular body with end edgeportions 12 and 14 deformed to provide outwardly flared flanges 16 and18 for engagement with container ends. The step of so deforming the edgeportions imposes severe stresses particularly in the seam area and ithas been found desirable that the adhesive of the seam allow limitedyield without rupture.

The completed container 20 (FIG. 6) includes end members 22 and 24 withedge portions 26 and 28 crimped around the flanges by an end seamingoperation.

Preferred operating conditions for efficient utilization of materialsand space in the manufacture of container bodies call for an in-lineoperation in which the bodies are formed with adhesive side seaming andare promptly passed to successive operations. In the manufacture of cansfor carbonated beverages, for example, beer cans, these operations mayinclude inside seam striping, interior lacquer coating and drying, endflanging, securing a bottom end member to the body portion by endseaming, filling, securing a top end member to the body portion by endseaming and pasteurizing. Through the in-line operation the necessityfor storing large quantities of container bodies is avoided and handlingof the bodies is reduced to a minimum.

The adhesive used in the method of the present invention meets therequirements imposed by in-line operation that the adhesive side seamdevelop strength rapidly on cooling from heat activated condition sothat it is not ruptured by the stresses imposed by the flangingoperations on the body, while at the same time the adhesive does notreach a stage in which it is completely unyieldable so that it is ableto accommodate minor relative movements between the overlapping portionswithout disruption of the adhesive bond or of the can body material. Theadhesive rapidly develops strength and heat resistance such that thetemperatures involved in drying a lacquer coating on its interior do notunduly weaken it to allow the seam to spring open under the stress ofthe resilience of the metal. The limited heating involved in drying thelacquer further hardens and strengthens the adhesive of the seam to apoint where it resists the interior pressures and temperatures involvedin the pasteurizing cycle. In this stage the adhesive also has anelement of resilience in the adhesive seam coupled with strongresistance to creep or bond separation under the substantial pressurescreated by the development of gas pressure within the sealed containerparticularly at high temperature, e.g. 150 F. to 160 F. at pasteurizing.

Development of successive stages of hardness and strength may beachieved through the combination of predetermined relative proportionsof a primary thermoplastic synthetic resin material possessingcontrolled crystallization ability and a synthetic polymer resin material which is amorphous and which cooperates both to give controlleddelay in crystallizing of the primary resin and to reinforce the primaryresin to give the desired strength and other physical properties in theadhesive bond. The resulting adhesive composition crystallizes only to alimited extent after application and formation of the seam so that itpossesses limited yieldability which allows sufficient movement suchthat it is not ruptured by the stresses imposed by flanging operationson the container body. Subsequently a short heating to a temperaturebelow the melting point of the adhesive, e.g. heating to dry an internallacquer coating causes crystallization within the adhesive compositionto proceed to a point giving greater strength and resistance to creep orbond separation under the pressures and temperatures involved, forexample, in pasteurization of the filled container. A further factor isthat the resin composition shrinks to a limited extent in the process ofcrystallization and this shrinkage occurs at a time when the metal ofthe container body is expanding under the action of heat. The resinmixture constituting the adhesive is caused to crystallize further at aslow rate even at the somewhat higher temperatures encountered inpasteurization so that the resin in the seam adapts itself to theexpansion of the metal in the container before crystallization proceedsto a point where the dimensions of the adhesive are fixed. At the sametime the crystallization which has developed provides strength and creepresistance necessary to withstand the rather susbtantial stressescreated by pressure developed within the container.

The crystallizing tendency of the polymer resin constituting the majorcomponent of the adhesive may be controlled at least in part by thecharacter of the polymer resin molecule. By way of illustration, apreferred type of polymer resin for the major component is anessentially linear mixed copolyester With a degree of regularitypermitting association of the molecule in orderly fashion to enablecrystallization. The polyester may be formed by condensation andpolymerization of dibasic acids and alkylene glycols having an evennumber of carbon atoms greater than 1 but not over 10. Suitable dibasicacids include terephthalic acid and isophthalic acid, and aliphaticdibasic acids having from 6 to 12 carbon atoms such as suberic acid,adipic acid and dodecanoic acid, azelaic acid, sebacic acid.Terephthalic acid, because of its structure of having carboxyl groupsarranged at opposite positions on a benzene ring is a factor tending toincrease the crystallizability of polymers containing it. Isophthalicacid gives a markedly lower rate of crystallization because of theout-of-line relation of the carboxyl groups on the benzene ring.Sebacic, azelaic and comparable aliphatic dibasic acids introducespacing between the benzene rings in the polymer chain and impart aflexibility to the polymer chain which aids in crystallization.Dimerized linoleic acids may also be included as a part of the acidcomponent where it is desired to introduce the effect of its relativelylong aliphatic chain. That is, the long chain of the dimerized acid doesnot aline in orderly fashion and provides an internal plasticizingaction and imparts a more resilient character to the polymer resin. Themajor polymer material is prepared with an initial softening point(preferably determined by the differential thermal analyzer), above themaximum temperature to which the adhesive will be subjected in use.

In general the molar ratio of terephthalic acid to isophthalic acid mayfall in the range of from about 12:1 to about 1:1 and there may bepresent up to about 35% of the aliphatic dibasic acid. As noted abovethe higher ratios of terephthalic to isophthalic increase the ability ofthe polymer to form strongly crystallized high melting bodies. On theother hand the presence of controlled amounts of the 6 to 12 carbon atomaliphatic dibasic acids allows crystallization but tends to give a lowermelting point resinous material. Particularly useful mixed polyestermaterials have included products of esterrfication and condensation of1,4-butane diol with terephthalic acid, isophthalic acid and 6 to 12carbon atom dibasic aliphatic acid suitably sebacic acid in the molarpercentages of about to 55%:15% to 2S%:8% to 25% respectively.

Following the principles outlined above the terephthalic acid,isophthalic acid and other acids may be combined in relative proportionsto give resins having controlled crystallization ability effective tosatisfy the requirements of melting point, strength and crystallizingaction in combination with the amorphous polymer resin for use as a sideseaming adhesive.

It is also possible to use more than one resin polymer to make up thecrystallizable component of the adhesive. Thus, it is possible to use aproportion of a resin polymer Which crystallizes at a moderate speed toprovide development of early green strength, i.e. strength within ashort time after completion of a seam to hold the parts together. Alongwith such moderate crystallization rate material there may be combinedresin polymers which crystallize more slowly so that, for example, thecrystallization of this portion of polymer is retarded until afterflanging and is available to harden the adhesive composition furtherwhen the rate of crysallization is accelerated by the heating involvedin drying the interior lacquer coating of a container.

The above discussion has related the development of stages of hardnessby crysallization. It is to be understood, however, that the developmentof stages of hardness and strength may also be obtained through thecombination of crystallization control and further polymerization ofresinous components or interreaction between resinous components, or mayinvolve such polymerization or interreaction alone. Systems for securingsuch development of properties can be readily devised by chemistsfollowing the teachings of the present case as to the advantagesobtained through such progressive development of properties.

Amorphous hard, strong polymeric material for cooperation with the majorpolymer material is selected to have a molecular structure which isrigid and relatively bulky while at the same time having components inthe molecular chain tending to associate with elements of the chain ofthe base polymer resin. Where the base polymer resin includes aromaticcomponents with benzene rings in the molecular chain it is desirablethat the amorphous polymer material also include such aro maticcomponents. A preferred material for this use is a phenoxy resinprepared by reaction of Bis-phenol-A with epichlorohydrin and havingrepeating units as follows:

where n is approximately 100.

With copolyester materials including terephthalic and isophthalic acidcomponents the aromatic rings of the phenoxy resin are capable ofassociating with the aromatic rings of the polyester. 'This givesstrength due to the boundary forces between these aromatic rings whenthe composition is in cool state. This factor also results in a lockingtogether of the aromatic rings of the phenoxy and polyester; and themolecular chain of the phenoxy resin is sufficiently rigid to preventinter-molecular slippage. A further advantage of the combination ofphenoxy resin with the polyester resin is a marked increase in adhesivebond strength of metal over the bond strength obtained with thepolyester resin alone.

On the other hand, when the composition including the polyester resinand the phenoxy resin i cooled from molten condition, the difference inspacing of the aromatic rings in the polyester resin and the phenoxyresin tends to retard the rate of crystallization of the polyester resinby interfering with normal orderly realinement of the equivalentconfigurations of adjacent polyester molecules.

Cooperation of the amorphous polymeric material with the crystallizablematerial to give the desired development of hardness through increasingextent of crystallization is controlled by the use of proper relativeproportions of these materials. In general from about 5% to about 50% ofthe amorphous phenoxy resin, preferably to 30%, based on the weight ofthe entire composition will give useful results. Determination of thebest relative proportions in a given case depends on the properties ofthe polyester resin material and on the conditions which it is requiredthat the adhesive be able to meet. Thus, with polyester resins having ahigh rate of crystallization it will be desirable to use a greaterproportion of the amorphous material in order to reduce the overallcrystallization rate of the adhesive mixture; and with slowercrystallizing polyester resins lower relative proportions of the phenoxyresin material will be used.

Excellent results are obtained with adhesive compositions comprising oneor more polyester resin materials in combination with the phenoxy resinwithout other additives. For special purposes, however, smallpercentages of other resin additives and small proportions andreinforcing or extending mineral fillers such as calcium silicate,silica aerogel and the like may be used.

The following examples are given to aid in understanding the invention;but it is to be understood that the invention is not limited to theparticular materials, conditions, procedures or products theredisclosed.

EXAMPLE I A mixed polyester resinous material was prepared fromesterification and condensation of 1,4-butane diol with dibasic acids.The total dibasic acid-s in the mixture were in the ratio of 6.2 mols ofterephthalic acid, 2.0 mols of isophthalic acid and 1.5 mols of sebacicacid. The melting point of the material was C. to C. (B and R).

A further polyester material was prepared through esterification andcondensation of 1,4-butane diol with acidic members in the ratio of 8mols of terephthalic acid and 2 mols of isophthalic acid. The meltingpoint of this resin was C. to 192 C. (B and R), and its rate ofcrystallization was markedly greater than that of the first polyesterresin material.

75 parts of the first polyester resinous material were melted andintimately mixed at 425 F. with 10 part of the second polyester materialand with 15 parts of phenoxy resin from reaction of bis-phenol-A withepichlorohydrin having repeating units as follows:

where n is approximately 100, the melting point of the phenoxy resinbeing about 212 F. The combination of resins had a melting point over325 F.

A blank B for a can body 2 in diameter 4 height was cut from 55 lb. basebox weight double reduced 0.25 lb. tin plate can stock, the blank having0.28 wide side seaming margins 8 and 10 free from lithography.

The blank was preheated to 350 F. to 400 F. and the adhesive compositionin molten state at 425 F. was applied as a 0.003 to 0.005 inch thickband 6 to the seaming margin 8 adjacent the edge 2 on the side i whichwill be on the interior of the can.

The blank while being maintained at about 350 F. to 400 F. was sent to aforming station where it was bent to cylindrical shape. The temperaturein the side seaming marginal areas 8 and 10 was raised to adhesiveactivation temperatures of 375 F. to 425 F. by an auxiliary heatingdevice and the seaming margins were pressed together with the heatactivated adhesive band 6 between them. Suflicient pressure was used tosecure over-all adhesive wetting of the seaming margins. The seam S washeld briefly while the adhesive cooled and set up.

The resulting cylindrical body was transported to a standard turret typeflanger where the end edge portions 12 and 14- were flared out toprovide flanges 16 and 18 to provide for receiving standard can ends 22and 24. The adhesive seam S withstood the shearing stress imposed bythis operation.

Lacquer was applied as a stripe to the interior along the seam area andthe entire interior of the body was then sprayed with a conventionalsolvent base lacquer. The can was sent to a drying tunnel where thelacquer was dried at 280 F. for 10 minutes. No loss of bond occurredduring the process. A first can end 22 was assembled with the body andthe body was end seamed and sent to a standard processing and fillingline including can turning, elevators, conveyors, accumulators and a 160F. sterilizing. The body was then filled, a second can end 24 wasapplied to the body and was end seamed to form a completed filled can.

The filled can was then put through a pasteurizing process whichinvolved subjecting to temperatures up to 160 F. or up to 30 minutes inthe course of which internal pressure of 85 to 90 lbs. per sq. inch wasdeveloped. No leaking or rupture of the can occurred.

Further cans prepared and filled as described above were stored at 42 F.and at 80 F. prior to being given test drops of from 4 to 5 feet. In allcases of failure during the drop test, the failure occurred in the endseams rather than in the side seams.

EXAMPLE II A polyester resinous material was prepared by esterificationand condensation of 1,4-butane diol with acidic components in the ratioof 9.8 mols of terephthalic acid, 0.87 mols of isophthalic acid and 0.13mols of linoleic acid dimer. The melting point of the polyester materialwas 375 F.

85 parts by weight of the above polyester were combined with parts byweight of the phenoxy resin used in Example I, mixing being carried outat 425 F. The resulting adhesive composition had a melting point of 365F.

The adhesive was used for side seaming of can stock following theprocedure set forth in Example I. Comparable results were obtained.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. The method for making tubular containers including the steps ofapplying to a side seaming surface portion of a metallic container blanka thermoplastic synthetic resin body having controlled delay hardeningability, forming said blank into a tubular body with said side seamingsurface portion disposed adjacent an opposite side seaming surfaceportion of said blank with said thermoplastic adhesive in heat-activatedcondition between said surface portions, pressing said surface portionstogether, cooling said adhesive to solidify it to hold said surfaceportions together as a completed seam, deforming portions of saidtubular body, treating said thermoplastic adhesive of said seam toincrease the hardness of said adhesive, thereafter attaching ends tosaid tubular body and treating said thermoplastic adhesive seam toharden it further, said thermoplastic adhesive comprising thermoplasticpolymer resin material having controlled hardenability, whereby limitedhardening occurs in the heat activation and seam completion step beforesaid deformation, further hardening is obtainable before end attachingand still further hardening is obtainable after end attaching.

2. The method for making tubular containers including the steps ofapplying to a side seaming surface portion of a metallic container blanka thermoplastic synthetic resin body having controlled delaycrystallization and hardening ability, forming said blank into a tubularbody with said side seaming surface portion disposed adjacent anopposite side seaming surface portion of said blank with saidthermoplastic adhesive in heat-activated condition between said surfaceportions, pressing said surface portions together, cooling said adhesiveto solidify it to hold said surface portions together as a completedseam, thereafter deforming end edge portions of said tubular body toform end attaching flanges, heating said thermoplastic adhesive of saidseam to harden said adhesive through controlled increase incrystallinity, thereafter attaching ends to said tubular body andheating said thermoplastic adhesive seam to harden it further throughfurther crys tallization, said thermoplastic adhesive comprisingthermoplastic polymer resin material having controlled hardenabilitywhereby limited hardening occurs in the heat ac tivation and seamcompletion step before said deformation, further hardening is obtainablethrough a further limited heating before end attaching and still furtherhardening after end attaching is obtainable through extended heating.

3. The method for making tubular containers as defined in claim 2 inwhich said thermoplastic adhesive comprises a mixture of thermoplasticpolymer resin having controlled hardenability through a restrictedcrystallization tendency and strong amorphous polymer resin compatiblewith said crystallizable first polymer resin and effective to reduce thecrystallizing tendency of said first resin whereby limited hardeningthrough crystallization occurs in the heat activation and seamcompletion step before end edge hanging, further hardening throughcrystallization is obtainable through a further limited heating andstill further hardening through crystallization is obtainable after endattaching through extended heating.

4. The method for making tubular containers as defined in claim 3 inwhich the thermoplastic adhesive is an intimate mixture of a hardamorphous phenoxy polymer resin having the following structure where nis about 100, and crystallizable resinous linear polyester of linearglycol and dibasic acid components, said acid components comprisingmixed terephthalic and isophthalic acids in the range of mol ratios offrom 12:1 to 1:1, said glycol having the formula HO(CH ),,'OH where n isan even number greater than 1 but not over 10, the benzene ringrepeating units of said phenoxy resin and said polyester resincooperating for reinforcement of the solidified adhesive, but said ringunits of said phenoxy resin having a different spacing in the molecularchain from the benzene rings in said polyester resin to retard alinementof the molecules of said polyester resin, and said phenoxy resin beingpresent in amount to delay development of crystallinity when saidadhesive is cooled from heat activated condition but not to preventcrystallization on heating of the adhesive to temperatures below itsmelting point.

5. The method for making tubular containers as defined in claim 4 inwhich the thermoplastic components of the adhesive comprise from about5% to about 50% by weight of said hard amorphous phenoxy resin polymerand from about 95% to about 50% of crystallizable resinous linearpolyester of linear glycol and dibasic acid components, said acidcomponents comprising at least about 65 mol percent of mixedterephthalic and isophthalic acids in the range of mol ratios of from12:1 to 1:1 and up to 35 mol percent based on the total acid componentsof an aliphatic dibasic acid having at least 6 carbon atoms, said glycolhaving the formula where n is an even number greater than 1 but not over10.

6. The method for making tubular containers as defined in claim 4 inwhich the resinous linear polyester of said thermoplastic adhesive is ablend of a polyester which crystallizes at a rate providing earlydevelopment of strength and a polyester which crystallizes more slowlyto allow development of further hardness at a later stage by heating toaccelerate its rate of crystallization.

7. The method for making tubular containers as defined in claim 5containing from 10 to 30% of said amorphous phenoxy resin polymer and90% to 70% of crystallizable polyester, said polyester comprising theproduct of esterification and condensation of 1,4-butane diol withacidic components in the molar percentages of from 70% to 55% ofterephthalic acid, from 15% to 25% of isophthalic acid and from 8% to25% of dibasic aliphatic acid having from 6 to 12 carbon atoms.

8. The method for making tubular containers as defined in claim 7 inwhich said resinous linear polyester is a blend of a polyester whichcrystallizes at a rate providing early development of strength and apolyester which crystallizes more slowly to allow development of furtherhardness at a later stage by heating to accelerate its rate ofcrystallization.

References Cited UNITED STATES PATENTS 2,679,305 5/ 1954 Gunthorp 220-812,799,610 7/1957 Magill 220-81 2,912,398 11/1959 Johnson et a1. 220-81RONALD D. GREFE, Primary Examiner.

U.S. Cl. X.R. 220

